<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
    <script src="./js/vue.js"></script>
    <style>
        .active{text-decoration: underline;}
        .text-danger{font-weight: bold;}
    </style>
</head>
<body>
    <div id="app">
        <div :class="[activeClass,errorClass]">Hello Vue!</div>
    </div>
</body>
<script>
    const vm=new Vue({
        el:'#app',
        data:{
            activeClass:'active',
            errorClass:'text-danger'
        }
    })
</script>
</html>